Câu hỏi 2

Ta có: \(L = 100 = 10.\log {I \over {{I_0}}} \Rightarrow {I_1} = {10^{ - 2}}({\rm{W}}/{m^2})\)

\(\left\{ \matrix{
{I_1} = {P \over {4\pi R_1^2}} \hfill \cr
{I_2} = {P \over {4\pi R_2^2}} \hfill \cr} \right. \Rightarrow {{{I_2}} \over {{I_1}}} = {\left( {{{{R_1}} \over {{R_2}}}} \right)^2} \Leftrightarrow {{{I_2}} \over {100}} = {\left( {{1 \over {10}}} \right)^2} = {1 \over {100}} \Rightarrow {I_2} = 1({\rm{W}}/{m^2})\)

Chọn C